Berkshire Hathaway's stock has underperformed the S&P 500 by 16.3% so far this year. Driven by popular technology stocks, the S&P 500 rose 5.1% in May, closing at a record high on Friday. In stark contrast, the share price of Berkshire Hathaway remained largely flat during the same month. Consequently, the widely held Class B shares of Berkshire have now trailed the S&P 500 by 16.3 percentage points year-to-date, marking the widest gap so far this year. At the end of March, Berkshire Hathaway's stock held only a slim 1.8 percentage point lead over the S&P 500. Since then, the S&P 500 has surged more than 35% in April and May, while Berkshire Hathaway's share price has declined by nearly 11%. Eager expectations for AI profits, coupled with massive investments in building the infrastructure required for future AI, have fueled significant gains in the dominant technology stocks within the market-cap-weighted S&P 500. On the other hand, Berkshire Hathaway has adopted an extremely conservative investment strategy, with minimal investment in AI, holding nearly $400 billion in cash reserves. Its operating companies generate steady profits but their performance is not particularly spectacular. If the enthusiasm for AI ultimately proves to be a bubble, as some have warned for months, this cautious approach could eventually pay off, much like Warren Buffett's avoidance of soaring internet stocks during the late 1990s. While the company's overall investment in the AI sector remains relatively small, the new CEO Greg Abel appears to have taken a step distinct from Buffett's style, tripling the company's stake in Alphabet during the first quarter. The Alphabet holding is now valued at nearly $22 billion, making it the fifth-largest stock position in the company's portfolio. Since hitting its record closing high last May, Berkshire Hathaway's share price has fallen by 12%. At that time, Buffett had just announced his plan to step down as CEO by the end of 2025. Chart analysis from 22V Research indicates that Berkshire Hathaway's relative performance against the S&P 500 has dropped to its lowest level since 2007. In a report to clients, 22V Research stated, "Berkshire Hathaway was once a good barometer for the S&P 500, but that relationship appears to be changing."